1. Field of the Invention
The present invention relates to objective lenses and endoscopes using the same.
2. Description of Related Art
With regard to endoscopes used in the medical field, there have been demands to reduce the diameter of insertion sections of the endoscopes and to shorten rigid ends of the insertion sections so as to improve maneuverability and to reduce the load on patients. Therefore, objective lenses mounted in endoscopes need to have a small outer diameter and a short overall length. Furthermore, in order to improve the diagnostic ability of endoscopes, it is important to enhance the image quality by correcting various kinds of optical aberrations. A compact, simple-structured endoscope objective lens corrected for chromatic aberration is known (for example, see Japanese Unexamined Patent Application, Publication No. 2007-249189, U.S. Pat. No. 6,956,703, and U.S. Pat. No. 5,587,839).